The rotary kiln is a cylindrical shell driven by a bull gear. There is a plurality of pads welded to the shell and these pads are approximately four inches thick by four inches wide. The pads each have an OD surface. There is also a tire having an inner face (ID surface) and the inner face is slipped onto the plurality of pads. The tire is supported by a plurality of trunnion supported rollers.
So as to allow for expansion and other movement between the tire and the pads, the OD surface of the pads is smaller than the ID surface of the tire. In other words, there are two dimensions; a large one being the tire and a smaller one being the kiln shell and pads. Because, there are two different dimensions, there is creep or slippage between the tire and the pads. If there is any friction between the ID surface of the tire and the OD surface of the pads, due to inadequate lubrication of these surfaces, the creep or slippage can increase and can cause many problems in the maintenance of the kiln. Therefore, it is necessary to lubricate the ID surface of the tire and the OD surface of the pads. The pads are separated by approximately four inches allowing a lubricant to lubricate the ID surface of the tire and the OD surface of the pads.
The combination of a polymer carrier containing antioxidants which prevent the metal of the shell from oxidising at a high temperature, thickening agents, powdered carbons and at least one soft metal namely (e.g. copper, zinc, aluminum), in order to produce a lubricating formula in liquid suspension is already well known and commonly used for lubricating, an ID surface of a tire and an OD surface of a plurality of pads, operating at temperatures from 100.degree. F. to 500.degree. F. or higher.
Hitherto, it has been common to have the carrier and the lubricant in a liquid or semi-liquid suspension. When the combination is in liquid suspension, it is applied to the inner surface of the tire by using hoses, pumps and a large keg that contains the liquid or semi-liquid suspension. The carrier evaporates at the temperature of the tire and releases a dry lubricant, leaving very little harmful residue on the tire.
The problem with using hoses, pumps and a keg to apply the lubricant in liquid suspension to the tire, is that it is a messy and elaborate job that takes some time to complete. Other problems that arise when using a liquid or semi-liquid lubricant is the distribution of pressurized air or electricity from pier to pier to operate the pump that is required to apply the lubricant to the ID surface of the tire and also the manoeuvring of the keg or drum from pier to pier on a grated catwalk spanning up to 700 feet in length. In many cases, there is no catwalk connecting the piers, so therefore the keg or drum must be hoisted approximately 32 feet in the air to reach the tire for lubrication.
It is also well known to provide a lubricant in the form of a solid graphite lubrication block, the block being inserted in between the pads, between the ID surface of the tire and the kiln shell. As the tire rotates with the kiln shell, the graphite block rubs against the high spots and the graphite coats the ID surface of the tire. But the graphite block often tu3nbles with the rotation of the tire, and therefore leaves an insufficient amount of graphite on the ID surface Of the tire Which then deposits the graphite on the OD surface of the pads, in order to prevent metal to metal contact. Therefore, the graphite block is an even less efficient lubricant than the liquid suspension. Furthermore, graphite in itself only becomes an efficient lubricant when it is on a machine like surface, where it may laminate, whereas both of the above mentioned surfaces are very porous and rough.